AttrNumber attnum);
static bool dependency_is_compatible_clause(Node *clause, Index relid,
AttrNumber *attnum);
-static MVDependency *find_strongest_dependency(StatisticExtInfo *stats,
- MVDependencies *dependencies,
+static MVDependency *find_strongest_dependency(MVDependencies **dependencies,
+ int ndependencies,
Bitmapset *attnums);
static void
* (see the comment in dependencies_clauselist_selectivity).
*/
static MVDependency *
-find_strongest_dependency(StatisticExtInfo *stats, MVDependencies *dependencies,
+find_strongest_dependency(MVDependencies **dependencies, int ndependencies,
Bitmapset *attnums)
{
- int i;
+ int i, j;
MVDependency *strongest = NULL;
/* number of attnums in clauses */
* fully-matched dependencies. We do the cheap checks first, before
* matching it against the attnums.
*/
- for (i = 0; i < dependencies->ndeps; i++)
+ for (i = 0; i < ndependencies; i++)
{
- MVDependency *dependency = dependencies->deps[i];
-
- /*
- * Skip dependencies referencing more attributes than available
- * clauses, as those can't be fully matched.
- */
- if (dependency->nattributes > nattnums)
- continue;
-
- if (strongest)
+ for (j = 0; j < dependencies[i]->ndeps; j++)
{
- /* skip dependencies on fewer attributes than the strongest. */
- if (dependency->nattributes < strongest->nattributes)
- continue;
+ MVDependency *dependency = dependencies[i]->deps[j];
- /* also skip weaker dependencies when attribute count matches */
- if (strongest->nattributes == dependency->nattributes &&
- strongest->degree > dependency->degree)
+ /*
+ * Skip dependencies referencing more attributes than available
+ * clauses, as those can't be fully matched.
+ */
+ if (dependency->nattributes > nattnums)
continue;
- }
- /*
- * this dependency is stronger, but we must still check that it's
- * fully matched to these attnums. We perform this check last as it's
- * slightly more expensive than the previous checks.
- */
- if (dependency_is_fully_matched(dependency, attnums))
- strongest = dependency; /* save new best match */
+ if (strongest)
+ {
+ /* skip dependencies on fewer attributes than the strongest. */
+ if (dependency->nattributes < strongest->nattributes)
+ continue;
+
+ /* also skip weaker dependencies when attribute count matches */
+ if (strongest->nattributes == dependency->nattributes &&
+ strongest->degree > dependency->degree)
+ continue;
+ }
+
+ /*
+ * this dependency is stronger, but we must still check that it's
+ * fully matched to these attnums. We perform this check last as it's
+ * slightly more expensive than the previous checks.
+ */
+ if (dependency_is_fully_matched(dependency, attnums))
+ strongest = dependency; /* save new best match */
+ }
}
return strongest;
Selectivity s1 = 1.0;
ListCell *l;
Bitmapset *clauses_attnums = NULL;
- StatisticExtInfo *stat;
- MVDependencies *dependencies;
Bitmapset **list_attnums;
int listidx;
+ MVDependencies **dependencies = NULL;
+ int ndependencies = 0;
+ int i;
/* check if there's any stats that might be useful for us. */
if (!has_stats_of_kind(rel->statlist, STATS_EXT_DEPENDENCIES))
return 1.0;
}
- /* find the best suited statistics object for these attnums */
- stat = choose_best_statistics(rel->statlist, STATS_EXT_DEPENDENCIES,
- list_attnums, list_length(clauses));
+ /*
+ * Load all functional dependencies matching at least two parameters. We
+ * can simply consider all dependencies at once, without having to search
+ * for the best statistics object.
+ *
+ * To not waste cycles and memory, we deserialize dependencies only for
+ * statistics that match at least two attributes. The array is allocated
+ * with the assumption that all objects match - we could grow the array
+ * to make it just the right size, but it's likely wasteful anyway thanks
+ * to moving the freed chunks to freelists etc.
+ */
+ ndependencies = 0;
+ dependencies = (MVDependencies **) palloc(sizeof(MVDependencies *) *
+ list_length(rel->statlist));
+
+ foreach(l,rel->statlist)
+ {
+ StatisticExtInfo *stat = (StatisticExtInfo *) lfirst(l);
+ Bitmapset *matched;
+ int num_matched;
+
+ /* skip statistics that are not of the correct type */
+ if (stat->kind != STATS_EXT_DEPENDENCIES)
+ continue;
+
+ matched = bms_intersect(clauses_attnums, stat->keys);
+ num_matched = bms_num_members(matched);
+ bms_free(matched);
+
+ /* skip objects matching fewer than two attributes from clauses */
+ if (num_matched < 2)
+ continue;
+
+ dependencies[ndependencies++]
+ = statext_dependencies_load(stat->statOid);
+ }
/* if no matching stats could be found then we've nothing to do */
- if (!stat)
+ if (!ndependencies)
{
pfree(list_attnums);
return 1.0;
}
- /* load the dependency items stored in the statistics object */
- dependencies = statext_dependencies_load(stat->statOid);
-
/*
* Apply the dependencies recursively, starting with the widest/strongest
* ones, and proceeding to the smaller/weaker ones. At the end of each
MVDependency *dependency;
/* the widest/strongest dependency, fully matched by clauses */
- dependency = find_strongest_dependency(stat, dependencies,
+ dependency = find_strongest_dependency(dependencies, ndependencies,
clauses_attnums);
/* if no suitable dependency was found, we're done */
s1 *= (dependency->degree + (1 - dependency->degree) * s2);
}
+ /* free deserialized functional dependencies (and then the array) */
+ for (i = 0; i < ndependencies; i++)
+ pfree(dependencies[i]);
+
pfree(dependencies);
pfree(list_attnums);
50 | 50
(1 row)
+-- check the ability to use multiple functional dependencies
+CREATE TABLE functional_dependencies_multi (
+ a INTEGER,
+ b INTEGER,
+ c INTEGER,
+ d INTEGER
+);
+INSERT INTO functional_dependencies_multi (a, b, c, d)
+ SELECT
+ mod(i,7),
+ mod(i,7),
+ mod(i,11),
+ mod(i,11)
+ FROM generate_series(1,5000) s(i);
+ANALYZE functional_dependencies_multi;
+-- estimates without any functional dependencies
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE a = 0 AND b = 0');
+ estimated | actual
+-----------+--------
+ 102 | 714
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE c = 0 AND d = 0');
+ estimated | actual
+-----------+--------
+ 41 | 454
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE a = 0 AND b = 0 AND c = 0 AND d = 0');
+ estimated | actual
+-----------+--------
+ 1 | 64
+(1 row)
+
+-- create separate functional dependencies
+CREATE STATISTICS functional_dependencies_multi_1 (dependencies) ON a, b FROM functional_dependencies_multi;
+CREATE STATISTICS functional_dependencies_multi_2 (dependencies) ON c, d FROM functional_dependencies_multi;
+ANALYZE functional_dependencies_multi;
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE a = 0 AND b = 0');
+ estimated | actual
+-----------+--------
+ 714 | 714
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE c = 0 AND d = 0');
+ estimated | actual
+-----------+--------
+ 454 | 454
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE a = 0 AND b = 0 AND c = 0 AND d = 0');
+ estimated | actual
+-----------+--------
+ 65 | 64
+(1 row)
+
+DROP TABLE functional_dependencies_multi;
-- MCV lists
CREATE TABLE mcv_lists (
filler1 TEXT,
SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE a = 1 AND b = ''1'' AND c = 1');
+-- check the ability to use multiple functional dependencies
+CREATE TABLE functional_dependencies_multi (
+ a INTEGER,
+ b INTEGER,
+ c INTEGER,
+ d INTEGER
+);
+
+INSERT INTO functional_dependencies_multi (a, b, c, d)
+ SELECT
+ mod(i,7),
+ mod(i,7),
+ mod(i,11),
+ mod(i,11)
+ FROM generate_series(1,5000) s(i);
+
+ANALYZE functional_dependencies_multi;
+
+-- estimates without any functional dependencies
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE a = 0 AND b = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE c = 0 AND d = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE a = 0 AND b = 0 AND c = 0 AND d = 0');
+
+-- create separate functional dependencies
+CREATE STATISTICS functional_dependencies_multi_1 (dependencies) ON a, b FROM functional_dependencies_multi;
+CREATE STATISTICS functional_dependencies_multi_2 (dependencies) ON c, d FROM functional_dependencies_multi;
+
+ANALYZE functional_dependencies_multi;
+
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE a = 0 AND b = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE c = 0 AND d = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies_multi WHERE a = 0 AND b = 0 AND c = 0 AND d = 0');
+
+DROP TABLE functional_dependencies_multi;
+
-- MCV lists
CREATE TABLE mcv_lists (
filler1 TEXT,
projects / postgresql.git / commitdiff